[stouset]

I let out a verbal "what the fuck" when I tried this. Same exact thing as you, it's absolutely striking.

[d4mi3n]

I was confused as well. First impression: nothing. Get up and look with both eyes and there it was. Interesting stuff.

[kolinko]

For me, if I focus intensely on the head, the neck stops moving. When I relax, and the reference naturally changes to the lines in the background, the neck begins moving again.